Study: Lose weight before knee surgery

Valley News Correspondent
Published: 3/11/2019 10:23:26 PM
Modified: 3/12/2019 1:05:29 PM

HANOVER — A team of Dartmouth researchers has found that morbidly obese patients undergoing knee replacement surgery have better outcomes if they lose at least 20 pounds prior to surgery. 

Benjamin Keeney, the study’s lead author, is presenting the research in a poster presentation Tuesday and Wednesday at the American Academy of Orthopaedic Surgeons’ 2019 annual meeting in Las Vegas.

The study’s conclusion might appear obvious. The morbidly obese experience more surgical complications, and their outcomes tend to be worse, so doctors recommend or even require weight loss before elective surgeries such as knee replacement. 

But in this study, Keeney looked at the effects of specific weight-loss targets that could be easily communicated to patients.

“Patients want to know, OK, you’re telling me to lose weight. How much weight should I lose? Give me a number,” said Keeney, who is an instructor at Dartmouth’s Geisel School of Medicine and has a doctorate in health services. 

The study examined data from 203 patients who were morbidly obese at least 90 days prior to surgery. Morbid obesity is generally defined as a person with a BMI, or body mass index, of 40 or above. A six-foot tall adult weighing 295 pounds has a BMI of 40.

In contrast to those who only lost five or 10 pounds, patients who lost at least 20 pounds before surgery were associated with shorter hospital stays, and lower odds of discharge to a nursing facility instead of being able to  go home. 

Fewer days in the hospital can translate into substantial cost savings. The average cost of an inpatient day at nonprofit hospitals in Vermont and New Hampshire is about $2,500, according to figures compiled by the Kaiser Family Foundation.

Keeney has found orthopedic surgeons to be generally receptive to his findings, and they’re happy to have a specific weight-loss target to share with their patients. But some still express concerns about operating on the morbidly obese due to higher complication rates.

“It’s a big ethical dilemma right now,” said Dr. David S. Jevsevar, the chair of Dartmouth-Hitchcock’s orthopaedics department and an author on the study. If a patient’s blood pressure is high enough, for example, a doctor may not find it safe to operate. Jevsevar says morbid obesity is a similar situation. 

“If they (the morbidly obese) have no complications, they do well,” Jevsevar said. “But we know that they are more likely to have complications.”

Jevsevar also wonders if patients’ engagement with their care, as evidenced by losing weight before surgery, may account for some of the study’s improved outcomes, or if the 20-pound figure will continue to hold up.

“We need to study this better,” he said. 

Keeney looks forward to larger studies like this that include more patients, and soon he’ll be digging into hip replacement data to see if there are similar benefits to pre-operative weight loss.

“This study is kind of opening up new questions, which is the entire point of research,” he said.

However, Keeney feels strongly that people shouldn’t be excluded from surgical procedures due to their weight. Losing weight is hard, and for some it may not be a real option. The injury that brought a patient to the orthopedic surgeon may be keeping them from engaging in physical activity.

There are other avenues to keep complication rates down, Keeney says, and his data show that surgeries like a knee replacement can really improve a person’s quality of life, regardless of their weight. So why wouldn’t you help them?

“People get a lot out of it,” he said.

Matt Golec can be reached at

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